1. Field of the Invention
The present invention relates to optical inspection and measuring systems, and more specifically, to an optical method and system for determining characteristics of optically recognizable surface features.
2. Description of the Related Art
Surface inspection systems are in widespread use in industries such as semiconductor and optical device manufacturing for verifying structures in design phases as well as during manufacturing quality inspection. Traditional surface inspection techniques rely on imaging a surface with multiple-pixel imaging systems and processing the resultant signals in order to detect features on the surface. A common surface inspection method uses a camera to capture an image of the entire surface of interest and processing the resultant two-dimensional image to identify surface features. The camera-based technique requires expensive equipment and complex image processing software or hardware. Further, the resolution of the system is limited by camera pixel count and size.
An alternative common method is surface scanning using a line array. The line array technique is generally less complex and expensive than imaging an entire surface. The resolution of a line array may be increased by increasing the pixel count or by joining multiple arrays. However, the scanning speed of the line array technique is limited by the access time required to address and read an intensity value from each pixel.
Inspection systems using a single detector element (point detector) have also been implemented, but while the cost of such elements is low and the access time of the detector is generally much higher than for a line array or camera, the time required for scanning and detecting resultant reflections from every unique point in two dimensions on a surface of interest limits the scanning speed of the point detector.
Therefore, it would be desirable to provide a low cost and high speed surface inspection system that does not require a camera or line array and that does not require a unique scan of every point on a surface of interest in order to detect surface features of the surface of interest.